Dualjet M2ME, M2MC Technical

1979 M2ME GENERAL APPLICATION:
  • Buick 3.2L (196"), 3.8L (231") V6
  • Chevrolet Passenger 3.2L (196"), 3.3L (200"), 3.8L (231") V6
  • Oldsmobile 3.8L (231") V6
  • Pontiac 3.8L (231") V6
1979 M2MC GENERAL APPLICATION:
  • Buick 4.9L (301"), 5.0L (305") V8
  • Chevrolet Passenger 4.4L (267"), 5.0L (305") V8
  • Chevrolet and GMC Truck 5.0L (305") V8
  • Oldsmobile 4.3L (260"), 4.9L (301"), 5.0L (305") V8
  • Pontiac 4.9L (301"), 5.0L (305") V8
As of 1979 the Dualjet M2MC is a new carburetor application for the 4.4L (267") and 5.0L (305") V8 engines. This carburetor replaces the 2GC, 2GV carbs previously used on the 5.0L engine. 
The Dualjet 210 model carbuetors include carryover design features except as follows:
  • Specific calibration to meet 1979 emissions and fuel economy standards
  • On carryover models for the 4.9L engine, the clean air purge feature, with internal delay valve, is not used on the front (primary) vacuum break unit and the choke housing is changed from aluminum to zinc material. These changes are made for improved control of choke mixtures during the engien warm-up period.
  • The black plastic limiter caps on the idle mixture needles are no longer used. To provide a tamper-resistant idle mixture setting, a hardened steel plug is staked in the idle mixture needle opening. These plugs are not to be removed unless required for cleaning or part replacement.
Rochester Dualjet Carburetor

1979 E2ME GENERAL APPLICATION:
  • Buick 3.8L (231") V6 California Automatic
  • Chevrolet Passenger 3.8L (231") V6 California Automatic
  • Oldsmobile 3.8L (231") V6 California Automatic
  • Pontiac 3.8L (231") V6 California Automatic


The Rochester Dualjet E2ME Model 210 carburetor, used with the computer controlled catalytic converter system on the 3.8L, 231", V6 engine is a controlled air/fuel ratio single stage carburetor of downdraft design with small 1 7/32" bores.

The model 210 carburetor includes special design features for optimum air/fuel mixture control during all ranges of engine operation.

An electrically operated mixture control solenoid, mounted in the float bowl, is used to control air and fuel metered to the idle and main metering systems of the carburetor. Fuel metering is controled by special stepped metering rods, operating in removable jets, positioned by a plunger in the mixture control solenoid. The plunger in the solenoid is controlled (or "pulsed") by an electrical output signal received from the electronic control module (ECM) - a small "on-board" computer. The ECM responding to an electrical signal from the oxygen sensor in the exhaust, energizes the solenoid to move the plunger (and rods) down to the lean position, or partially energized, up to the rich position to control fuel delivery to the idle and main metering systems. At the same time, air metering to the idle system is controlled by an idle bleed valve, located in the air horn, which follows movement of the mixture control solenoid plunger to control the amount of air bled intot he idle system to lean or richen the mixtures. The movement (or "cycling) of the solenoid plunger, down (lean) or up (rich) occurs ten times per second, thereby controlling fuel and air mixtures to achieve, as near as possible, ideal air/fuel mixture ratios.

In this way, exhaust gas mixture oxygen content (lean or rich) is constantly monitored by the catalytic converter system and air/fuel mixtures adjusted accordingly for improved exhaust emissions and good engine performance.

The carburetor has internally balanced venting through two "D" shaped vent holes cast in the air horn (next to the idle air bleed valve), and a vent slot in the air horn, which are located directly over the float chamber.

It is also externally vented through a tub in the air horn which vents fuel vapors from the carburetor float bowl to the vapor canister to meet evaporative emission requirements.

An exhaust gas recirculation system (EGR) is used on all applications to control oxides of nitrogen. The vacuum supply port necessary to operate the recirculation valve is located in the throttle body and connects through a hose to the EGR valve.

The E2ME has six basic systems: float, idle, main metering (part throttle), main metering (wide-open), pump, and choke.

Rochester Dualjet Carburetor FAQ

Q: What is the Rochester Dualjet carburetor?
A: The Rochester Dualjet is a two-barrel (2GC) carburetor produced by Rochester Products, a division of General Motors. It is designed to provide efficient fuel delivery and improved throttle response in a compact package, commonly found on many GM vehicles from the mid-1970s through the 1980s.

Q: What makes the Dualjet carburetor unique compared to other carburetors?
A: Unlike conventional two-barrel carburetors, the Dualjet features two identical primary venturis and omits the secondary barrels entirely, making it lighter, simpler, and easier to service. It offers a good balance between performance and fuel economy for small- and mid-size engines.

Q: Which vehicles commonly used the Rochester Dualjet carburetor?
A: The Dualjet was used on various General Motors cars, including Chevrolet, Pontiac, Oldsmobile, Buick, and GMC light trucks, especially during the late 1970s and 1980s.

Q: How does the choke system work on the Dualjet carburetor?
A: The Dualjet can use either a manual or automatic choke. The automatic choke typically operates with a thermostatic spring (sometimes heated by an electric element or hot air from the manifold), closing the choke plate for cold starts and gradually opening it as the engine warms up.

Q: What are the main adjustments on the Rochester Dualjet?
A: Typical adjustments include idle speed, idle mixture screws, and (on some models) the choke and fast idle. Float height, accelerator pump stroke, and the choke pull-off are also adjustable according to the vehicle’s service manual.

Q: What are common symptoms of a faulty Dualjet carburetor?
A: Common symptoms include rough idle, stalling, poor acceleration, hard starting, excessive fuel consumption, or hesitation during throttle application. These issues often relate to clogged jets, vacuum leaks, incorrect adjustments, or worn components.

Q: How do you clean and maintain a Rochester Dualjet carburetor?
A: Regular maintenance includes checking and adjusting the float, inspecting the accelerator pump, and cleaning all jets, passages, and filters. During a rebuild, all gaskets and rubber components should be replaced using an appropriate kit, and all parts should be cleaned with carburetor-safe solvent.

Q: Are there any special considerations when rebuilding a Dualjet carburetor?
A: Yes. Always use new gaskets, O-rings, and rubber parts from a quality rebuild kit. Avoid using metal tools to clear jets or passages, as this may damage them. Pay attention to float settings and ensure all linkages move freely.

Q: Where can I find more detailed instructions or diagrams for the Rochester Dualjet?
A: Detailed service procedures, exploded diagrams, and specifications are available in the official service manual and reputable sources such as carburetor-parts.com.


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